But in an interview with Personnel Today, Prentis said: “I don’t believe there is a risk of unions withdrawing support for Brown.

“I have a very strong belief that as a general secretary, it’s not my role to seek to change the leader of the party or the prime minister, and I can assure you we are not seeking a change in leadership.”

He added that MPs were unlikely to vote against Brown in a leadership contest as the public outcry at a second unelected prime minister could lead to a general election – risking their seats.